For this third Air Force launch of a lunar orbiter, engineers introduced a number of changes to the Thor-Able launcher.

The probe included a new TV scanner and a new type of battery, as well as a new cosmic-ray telescope to study the Cherenkov Effect.

Pioneer 2, like its predecessors, never reached its target. A signal from the ground shut down the Thor launch vehicles stage 2 earlier than planned. Additionally, when the X-248 third stage engine separated, it failed to fire. As a result, the probe burned up in Earths atmosphere only 45 minutes after launch.

During its brief mission, it reached an altitude of 1,550 kilometers and sent back data that suggested that Earths equatorial region had higher flux and energy levels than previously thought. The information also indicated that micrometeoroid density was higher near Earth than in space.

Investigators concluded that the third-stage engine had failed to fire because of a broken wire.

Key Dates

8 Nov 1958: Launch

Status: Unsuccessful

Fast Facts

The Cherenkov Effect is caused by high-energy beta particles moving at velocities faster than the speed of light in water.

The effect causes the blue glow in nuclear reactors (right).

This process is similar to the sonic boom heard when an airplane exceeds the speed of sound.